Problem 3.4: Energy required in a proton-proton collision to produce a proton anitproton pair?

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Pick a reference frame to view the creation of an antiproton from a collision of two protons. When the two protons collide, they create three protons and one antiproton (same mass as proton, but opposite sign). The rest mass of a proton (and anti-proton) is 938 MeV/c2.  In the laboratory frame, the kinetic energy of the incoming particle (red) on the target (blue) is called the threshold kinetic energy to produce this reaction. Restart.

  1. In the laboratory frame, what is v/c for the red particle?
  2. What is v/c for the reaction products (the yellow and green particles)?
  3. What is the kinetic energy of the red particle (the threshold energy)?  The Bevatron accelerator at the Lawrence Berkeley Laboratory was designed to give a proton this threshold kinetic energy to produce this reaction. Emilio Serge and Owen Chamberlain won the 1959 Nobel prize in physics for carrying out this experiment and their discovery of the antiproton as a result.2

2See discussion in K. Krane, Modern Physics, John Wiley & Sons (1996), pp. 50-51.


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